When a terminal is in a connected state, a source cell provides value of a mobility control parameter for the terminal, and the source cell may hand over the terminal to a target cell:
if the handover fails, the terminal may select a reestablished cell and reestablish a radio link with the reestablished cell; or
if the handover succeeds but a radio link connection failure occurs between the terminal and the target cell later, the terminal may also select a reestablished cell and reestablish a radio link with the reestablished cell.
In the foregoing two cases, the reestablished cell may be the source cell, or the target cell, or a cell other than the source cell and the target cell.
The mobility control parameter sent by the source cell after the terminal establishes a connection with the source cell may include a handover control parameter, a terminal moving state control parameter, a target cell size control parameter, and so on. The handover control parameter includes time to trigger (Time To Trigger) a measurement event, an offset of the measurement event, layer 1 filtering time T, a layer 3 filtering coefficient K, and so on. The terminal moving state control parameter includes a scale factor sf-High corresponding to a high moving state, a scale factor sf-Medium corresponding to a medium moving state, and so on. The target cell size control parameter includes a scale factor sf-Large corresponding to a large cell, a scale factor sf-Small corresponding to a small cell, and so on.
The terminal detects its moving state, and selects a corresponding scale factor according to its moving state to scale the handover control parameter. Using Time To Trigger as an example:
when the UE detects that the UE itself is in the high moving state, the UE scales the handover control parameter as follows:Time To Trigger 1=Time To Trigger×sf-High;
when the UE detects that the UE itself is in the medium moving state, the UE scales Time To Trigger as follows:Time To Trigger2=Time To Trigger×sf-Medium;
when the UE detects that the UE itself is in a normal moving state, the UE does not scale Time To Trigger.
Definitely, Time To Trigger is merely used as an example for description herein. Other handover control parameters may also be scaled in the preceding manner.
After scaling is performed according to the moving state, the UE determines the size of the target cell, and selects a corresponding cell size scale factor according to the size of the target cell to scale the handover control parameter. Still using Time To Trigger as an example:
after scaling is performed according to the moving state, for example, after scaling is performed according to the high moving state, when the UE determines that the target cell is a large cell, the UE scales Time To Trigger3 as follows:Time To Trigger3=Time To Trigger1×sf-Large;
after scaling is performed according to the moving state, for example, after scaling is performed according to the medium moving state, when the UE determines that the target cell is a small cell, the UE scales Time To Trigger4 as follows:Time To Trigger4=Time To Trigger2×sf-Small;
when the UE determines that the target cell is a normal cell, the UE does not scale Time To Trigger any longer.
Definitely, whether scaling according to the moving state is performed first or scaling according to the cell size is performed first has no impact on the final scaling effect, and the sequence may be reversed.
The UE uses the scaled handover control parameter to control the current handover process.
The mobility control parameter in the prior art have a great impact on moving performance of the UE. To achieve a better balance between a UE link connection failure rate and a UE ping-pong handover rate, a base station in the prior art needs to perform a lot of outdoor tests, data collection, and statistical analyses to determine proper values of these control parameters beforehand, and is incapable of automatically adjusting the mobility control parameter used by the terminal.